This application claims the priority of French application FR/01.02279, filed Feb. 20, 2001, the entire disclosure of which is incorporated herein by reference.
The invention relates to the field of sports involving gliding over snow and, more particularly, downhill skiing. It relates more specifically to downhill skis of which the topsheet in the underfoot zone is not totally planar, but, on the contrary, has lateral recesses in the region of the upper ridges.
Generally speaking in its underfoot zone, a downhill ski has at least one lower gliding surface composed of a sole plate bordered by metal edges. It also includes a topsheet which is substantially parallel to the lower gliding surface, on either side of the longitudinal center plane of the ski.
There are two main families of structures which make it possible to produce current downhill skis.
In a first family, the structure includes lateral reinforcement elements which form at least one part of the lateral faces of the ski. These reinforcement elements are generally visible and form the sides of the ski over all or part of its thickness. These reinforcement elements are located in line with the edges and, more precisely, the thicker part of the edges which is adjacent to the gliding sole plate, also known as the xe2x80x9cbeadxe2x80x9d. Thanks to these reinforcement elements, the bearing forces exerted on the topsheet of the ski are more efficiently transmitted to the edges and thus allow better gripping.
In a second family, the structure comprises a shell of trapezoidal general section, which connects one edge to the other by capping the component elements of the structure.
Described in document EP 0 744 196, which corresponds to document U.S. Pat. No. 5,944,336, is a board for gliding which has such a shell structure and which also has recesses made in the region of the lateral faces extending between the edges and the topsheet of the ski.
More precisely, the ski described in this document has a height differential between the central part of its topsheet and the lateral zones. This differential forms a recess made above the edge.
This recess has a depth that is substantially constant over its entire length, so that it has a base that is substantially parallel to the gliding sole plate.
The aim of the invention is to provide a ski which has a geometry derived from that described above and with superior dynamic behavior qualities, particularly regarding the linking of the various phases of a turn.
The invention thus relates to a board for gliding for downhill skiing which in a known manner, has, at least in its underfoot zone:
a lower gliding surface composed of a sole plate bordered by metal edges;
a topsheet substantially parallel to the lower gliding surface, on either side of the center longitudinal plane of the board;
lateral faces extending between the metal edges and the topsheet, said lateral face having recesses located below the plane of the topsheet and opening out in the latter.
According to the invention, this board is noteworthy in that the base of the recesses forms a slope that is inclined longitudinally relative to the lower gliding surface and the topsheet.
In other words, the characteristic recesses form a hollowed zone inside the lateral faces which thus have a reduced height that can vary in the region of these recesses. The board thus has, in this region, a continuous diminution in its thickness. This gives rise to a partial and localized variation of stiffness in the zone of the recess. Consequently, the behavior of the board is modified as a function of the location of the point of application of the forces exerted by the skier, this location depending greatly, in particular, on the position adopted by the skier during the various phases of a turn.
The characteristic recesses may assume different shapes.
Thus, the lower part of the recesses, i.e. their base, may be inclined either toward the front and the bottom of the ski or toward the rear and the bottom of the ski. In this latter case, the gradient of the longitudinal section in the lateral face moves the bearing pressure toward the front of the ski during a turn since the partial stiffness of the ski is greater to the front than to the rear of the recess. This therefore improves execution of the turn because edge-gripping during initiation of the turn is more efficient.
The inclined slope of the base of the recesses may also have various geometries. Thus, the lower part of the recesses may have a slope which is either substantially constant over the greater part of its length or, alternatively, a slope that can vary over the length of the recess. In other words, the inclined base of the recess may be either planar or curved.
According to another characteristic of the invention, the lateral faces include lateral zones which can include different materials, in front and to the rear of the characteristic recess. The choice of different materials makes it possible to confer different mechanical properties on the zones directly to the front and to the rear of the characteristic recess.
Thus, in a first embodiment, one of the materials present in one of the lateral zones may be of a viscoeleastic nature, so as to confer damping properties on the lateral zone in question.
Conversely, one of the materials present in the lateral zones may be of an elastic nature, so as to confer dynamizing properties on the lateral zone in question.
These particular materials may be incorporated into the lateral zones as a function of the different geometries. Thus, when this is, for example, a viscoelastic material, this may be incorporated into the ski in the form of a spindle piece arranged between the lower part of the shell and the edge.
When this is an essentially elastic material, this may form a number of elements located inside slots made in the lateral zone in question, between the lower part of the shell and the edge. In this way, when the board bends, the various slots tend to open up, stretching the material contained therein. When the cause of the bending disappears, the elastic elements located inside the slots exert a force which tends to close up the slot so that it regains its initial geometry. This acceleration of the return into position is thus reflected in a dynamizing of the board, which favors more sports-style skiing.
In practice, the slots may have a V- or Y-shaped profile, or a rectangular profile or, alternatively, a combination of these various geometries.
According to the type of behavior it is desired to obtain, the zone having damping properties is located either to the front or to the rear of the recess, and the zone having dynamizing properties either to the rear or to the front of the recess.
In a particular embodiment, the characteristic recesses may have a width, measured transversely to the board, which can vary over the length of the recess. It is thus possible to optimize the partial variation in stiffness of the board.
In certain variant embodiments, the board for gliding may include a number of recesses made on the same side of the board. These recesses, numbering two or three, may have gradients oriented in the same direction or, in a preferred embodiment, in opposite directions.
Thus, in a particular embodiment, the board has two recesses on each side. The recess located to the front has a gradient oriented toward the bottom and toward the front. The recess located at the rear has a gradient oriented toward the top and toward the front (or, in an equivalent manner, toward the rear and toward the bottom.)
Such a board may, in particular, be equipped with a raising platform for the binding, which includes lateral portions of which the lower edge comes into contact or faces the base of the recess, with an inclined slope which complements that of the base of the recess.